1. Technical Field
This invention relates to a surface-emitting semiconductor array device, module, light source device, data processing apparatus, light transmitting device, light spatial transmitting apparatus, and light spatial transmitting system.
2. Related Art
A Vertical-Cavity Surface-Emitting Laser diode (hereinafter referred to as VCSEL) is a type of laser diode that emits light from a surface of a semiconductor substrate. As compared with edge-emitting laser diodes, VCSELs require a lower current for driving. Another advantage includes that a nondestructive evaluation, i.e., a wafer-level evaluation, can be performed; and VCSELs can be easily arranged two-dimensionally. Therefore, VCSELs have been used for light sources for optical data processing apparatuses, optical communication devices, or data storage apparatuses using light.
FIG. 16 schematically illustrates an electrode structure of a VCSEL of a related art. In FIG. 16, on a substrate 10 of such as GaAs, a mesa- or post-shaped light-emitting portion 12, and an electrode pad portion 16 isolated by a dividing groove 14 from the light-emitting portion 12 are formed. The light-emitting portion 12 includes plural semiconductor layers (not shown) stacked on the substrate, and on a top portion thereof, an electrode layer 18 is formed. The electrode layer 18 forms a window (opening portion) 20 for emitting laser light at a top portion the light-emitting portion 12, and allows current injection into the light-emitting portion 12. The sidewall of the light-emitting portion 12, the dividing groove 14 and the electrode pad portion 16 are covered with an interlayer insulating film 22. The electrode layer 18 is connected to an electrode pad 24 by a metal wire 18a formed on the interlayer insulating film 22. To the electrode pad 24, a metal ball 26 is bonded, and a bonding wire 28 connected to the metal ball 26 is connected to a mount member, lead frame, or the like.
When a certain pressure or vibration is applied to the electrode pad 24 during bonding of the metal ball 26, the electrode pad 24 or the metal wire 18a may peel off from the interlayer insulating film 22. The pressure or vibration may also cause the interlayer insulating film 22 to be easily released from the underlying semiconductor layer.
As shown in FIG. 17, in the electrode configuration of a VCSEL array of a related art, a side wall 14a of the dividing groove 14 that divides the light-emitting portion 12 and the electrode pad portion 16 is a straight line. With such simple shape, pressure or vibration during bonding easily propagates, and there has been an issue in that the electrode pad 24 (metal wire 18a) or the interlayer insulating film 22 may peel off, especially in the vicinity of a stepped portion A of the electrode pad portion 16.
In addition, in a case where the light-emitting portion 12 and the electrode pad portion 16 are closely positioned in a substrate plane, pressure or vibration during bonding may propagate through the interlayer insulating film 22 that covers the substrate surface, and thus propagate close to the light-emitting portion 12, and the metal wire 18a or the electrode layer 18 routed in the dividing groove 14 may peel off from the interlayer insulating film 22. Such event significantly reduces the reliability of the VCSEL array, and is undesirable.
The present invention aims to improve adhesion of a metal wiring, electrode pad, and interlayer insulating film, and provide a small and highly reliable surface-emitting semiconductor array device.